The invention relates to improvements in blinds, and more particularly to improvements in blinds with vertical slats.
A blind with vertical slats normally comprises a support in the form of an elongated rail which defines an internal track for a row of carriers in the form of trolleys which are movable along the track. The trolleys support connecting elements which carry the upper end portions of vertical slats, and the trolleys can be moved longitudinally of the rail by means of a cord. A shaft or a like motion-transmitting part is provided to turn the connecting elements about vertical axes in order to change the orientation of the slats, namely the extent to which neighboring slats overlap or the extent to which neighboring slats permit light and/or air to pass between them. Neighboring trolleys of the rod are connected to each other by suitable distancing elements.
If a blind of the above outlined character is used to prevent penetration of light into or from a room, for example, to prevent penetration of daylight or other outside light into a room which is to be used for projection of images of film frames or diapositives onto a screen, even the slats are made of an opaque plastic or other material. This can detract from the appearance of the room or from the appearance of the building in which the blind with dark slats is put to use. Moreover, it is necessary to clean the slats from time to time, and any thorough cleaning involves detachment of the slats from the respective trolleys. Therefore, persons walking past a window or door which is equipped with a blind having vertical slats, or persons looking at the door or window from neighboring buildings, have practically unobstructed view of the activities in the room as long as the slats remain detached from their carriers. This is often highly undesirable, for example, if the room is a conference room or an office for conducting confidential discussions and/or for displaying objects which should not be seen by unauthorized persons and/or for divulging (e.g., displaying) information which is to remain confidential.